First he complimented Barack Obama’s “tan”, then he played hide and seek with the German leader. He has even annoyed the Queen by being too loud.

Now gaffe-prone Italian Prime Minister Silvio Berlusconi has held up the start of a key Nato summit – by talking for too long on his mobile phone.

German Chancellor Angela Merkel waited on a red carpet for several minutes looking bemused as the call dragged on.

She finally opted to start the event’s opening ceremony without the Italian.

In a symbolic show of unity and peace in Europe that Nato has helped to defend to mark the bloc’s 60th anniversary, the summit is being jointly hosted by Germany and France on the River Rhine which divides the two countries.

Mrs Merkel led other Nato leaders from Germany across a bridge straddling the river to meet President Nicolas Sarkozy coming from Strasbourg on the French side.

Mr Berlusconi joined the group shortly afterwards.

An Italian government source said he had been talking to the Turkish delegation in an attempt to settle a dispute over who should be the alliance’s next secretary general.

Playboy tactics

The Italian leader has developed a reputation for gaffes, outspoken comments and playful behaviour, even on the world stage.

The latest incident comes just days after the Queen appeared to express mild irritation when Mr Berlusconi noisily greeted US President Barack Obama at a photo-call in London.

Last year he was filmed apparently playing “hide and seek” with Mrs Merkel in Trieste, hiding behind a large column as she walked past.

Earlier, he came under fire for describing Barack Obama as “young, handsome and tanned”. Mr Berlusconi has palmed off the criticism those comments prompted, saying it emanated from humourless “imbeciles”.

Mr Berlusconi’s previous practical jokes at formal gatherings include making the Italian horned cuckold gesture behind a Spanish minister during a group photo of EU leaders in 2002.

The billionaire media mogul then sparked a minor diplomatic incident in 2005 by suggesting he had used “playboy tactics” to woo Finnish President Tarja Halonen in order to ensure her backing for Italy to host the European Food Safety Authority.